DN85

DN85 ZXSC400 1W/3W buck LED drivers Ray Liu, Applications Engineer, Zetex Semiconductors Description In Figure 1, ZXSC400 is configured as a high efficiency buck LED driver. The target applications are either 1W (350mA) or 3W (700mA) drivers for white LED driven from a 4 cell battery, or a 2 alkaline cell input for flashlights. The supply voltage for ZXSC400 reference design is: VIN = 3.8V to 6V. Parts lists for 1W and 3W design are shown in Table 1 and Table 2 respectively. Performance data is measured based on two different LED's VF binning with 0.3V VF difference. C3 VIN = 4V to 6V L1 D1 C2 U1 VCC Stdn VDRIVE VFB ISENSE Q1 R3 R2 C1 GND ZXSC400 R1 Figure 1 Schematic diagram Issue 1 - August 2007 © Zetex Semiconductors plc 2007 1 www.zetex.com DN85 Ref. Value U1 Q1 D1 L1 R1 R2 R3 C1 C2 C3 N/A N/A Package Part number SOT23-6 ZXSC400E6 SOT23 Manufacturer Contact details Zetex www.zetex.com www.zetex.com www.zetex.com Notes LED Driver Low sat NPN transistor 40V/0.75A Schottky diode ZXTN25012EFL Zetex BAT750 744052470 Zetex Wurth Elektronik Generic Generic Generic Generic Generic Generic Table 1 40V/0.75A SOT23 47␮H 62m⍀ 10⍀ 47⍀ N/A 0805 0805 0805 www.we-online.com ISAT = 520mA N/A N/A N/A N/A N/A N/A 0805 1% 0805 5% 0805 5% X7R/X5R COG/NPO X7R/X5R optional 4.7␮F/10V 1206 100pF/10V 0805 1uF/10V 0805 Bill of materials for 1W LED www.zetex.com 2 Issue 1 - August 2007 © Zetex Semiconductors plc 2007 DN85 Performance 100 90 0.5 0.4 Output Current (A) VF~3.3 VF...